Limitations of AAV vectors include inefficient production methods, packaging size constraints (introduced gene no larger than 4.5 kb), and a high level of immunity to AAV among adults (although AAV infection is not associated with any disease). The first AAV vectors were produced by transfection of 293 cells with two plasmids (an AAV vector plasmid and an AAV helper plasmid), and infection with adenovirus (reviewed in Muzyczka, (1992) Curr. Topics Microbiol. Immunol. 158:97-129). This method provided the essential elements needed for AAV vector production, including AAV terminal repeat (TR) sequences flanking a gene of interest, AAV helper functions consisting of the rep and cap genes, and adenovirus genes.
Improvements to the basic method have included: delivery of adenovirus genes by transfection to eliminate contaminating adenovirus (Grimm et al. (1998) Hum. Gene Ther. 9:2745-2760, Matsushita et al. (1998) Gene Ther. 5:938-945, Xiao et al. (1998) J. Virol. 72:10222-10226); delivery of AAV vector sequences within an Ad/AAV hybrid vector to increase vector production (Gao et al. (1998) Gene Ther. 9:2353-2362, Liu et al. (1999) Gene Ther. 6:293-299); and construction of first generation packaging cell lines containing the AAV rep and cap genes (Clark et al. (1995) Hum. Gene Ther. 6:1329-1341, Gao et al. (1998) Gene Ther. 9:2353-2362, Inoue & Russell (1998) J. Virol. 72:7024-7031, Liu et al. (1999) Gene Ther. 6:293-299, Tamayose et al. (1996) Hum. Gene Ther. 7:507-513, Yang et al. (1994) J. Virol. 68:4847-4856).
Glycogen storage disease type II (GSD II) presents as a classical lysosomal storage disorder, characterized by lysosomal accumulation of glycogen and tissue damage, primarily in muscle and heart (Hirschhorn et al. (2001) Glycogen Storage Disease Type II: Acid α-Glucosidase (Acid Maltase) Deficiency, p. 3389-3419. In C. R. Scriver, A. L. Beaudet, W. S. Sly, and D. Valle (eds.), The Metabolic and Molecular Basis for Inherited Disease. McGraw-Hill, N.Y.). Administration of a modified adenovirus vector encoding murine GAA or hGAA that was targeted to mouse liver reversed the glycogen accumulation in a GAA-knockout (GAA-KO) mouse model for Pompe disease within days, although the effect diminished with time (Amalfitano et al. (1999) Proc. Natl. Acad. Sci. U.S.A. 96:8861-8866, Ding et al. (2001) Hum. Gene Ther. 12:955-965, Pauly et al. (2001) Human Gene Ther. 12:527-538). AAV vectors have reversed the abnormalities in mouse models for hemophilia B (Snyder et al. (1999) Nat. Med. 5:64-70 [see comments]), Sly disease (Daly et al. (1999) Proc. Natl. Acad. Sci. U.S.A. 96:2296-2300), and for Fabry disease (Jung et al. (2001) Proc. Natl. Acad. Sci. U.S.A. 98:2676-2681) with long-term benefits, but not yet for GSD II.
In accordance with the present invention, highly increased AAV vector packaging with a hybrid Ad-AAV vector has been observed, and a modified adenovirus has been utilized, such that no contaminating Ad particles are produced during AAV packaging. Both the Ad and AAV versions of the vector encoding hGAA have been administered to the GAA-KO mouse model for GSD II. The hybrid Ad-AAV vector provides advantages for the development of gene therapy for GSD II, including but not limited to: (a) transgene delivery in vivo; (2) improved packaging of an AAV vector that delivered human GAA in the GAA-KO mouse; and (3) a combination thereof.